A workpiece such as a 300-mm diameter silicon ingot is mainly sliced in a conventional loose-abrasive-grain manner, in which the workpiece is sliced while supplying slurry containing suspended abrasive grains composed of, for example, silicon carbide to a wire. This manner takes 20 to 25 hours for slicing when using silicon carbide abrasive grains with a grit size of #1000 to #1500 (average abrasive grain diameter: about 8 to 10 μm).
It has been recently said that high integration of semiconductor devices such as DRAM, NAND flash memory, and MPU approaches technical limits, and cost reduction per silicon semiconductor device by miniaturization accordingly reaches its limit. In view of this; diameter enlargement to 450 mm is considered to yield more semiconductor devices from one wafer and continuously reduce the cost.
When the 450-mm diameter silicon ingot is sliced in the loose-abrasive-grain manner with abrasive grains such as silicon carbide grains, it essentially takes 40 to 50 hours for slicing along with the increase in area of the silicon ingot. This significantly reduces productivity per wafer.
Then, slicing the 450-mm diameter silicon ingot uses a fixed-abrasive-grain wire having diamond abrasive grains fixed to a core wire, which is employed to slice ingots for solar cells such as silicon, glass, magnet, crystal, sapphire, and silicon carbide (SiC) ingots (see Patent Document 1) A typical fixed-abrasive-grain wire is produced by fixing diamond abrasive grains with a minimum diameter of 4 μm and a maximum diameter of 16 μm on the surface of a metal core wire with a diameter of about 0.1 mm by electrolytic plating.
Slicing an ingot with the fixed-abrasive-grain wire uses a usual multi-wire saw to slice the ingot by pressing the ingot against the wire while supplying a coolant containing no abrasive grain to the travelling fixed-abrasive-grain wire. Compared with the conventional loose-abrasive-grain slicing manner, in which the ingot is sliced while supplying slurry containing suspended abrasive grains composed of, for example, silicon carbide with an average abrasive grain diameter of about 10 μm to the wire, the above manner can shorten the slicing time to half to one-third. Also, disuse of loose abrasive grains provides great advantages of the reduction in costs required for separating abrasive grains and metal powder or disposing a waste liquid used in slicing.